The goal of the project is to elucidate the biochemical requirements for plasticity in the formation of binocular cells in cortex during the critical period (CP). It is hoped that a biochemical understanding of this normal developmental process would give clinical guidance in considering how to aid individuals with permanent impairments (e.g. uncorrected congenital esotropia, cortical blindness) by boosting the plasticity through modifications of the chemical milieu of the brain. Kasamatsu's data indicate that the local concentration of catecholamines or of cAMP in the cortex can alter plasticity for binocularity. This possibility is examined in developing cats' visual system (untreated by drugs). The catecholamine concentration, activities of enzymes involved in cAMP metabolism, and the stimulation of the enzymes by the catecholamines will be examined in areas 17, 18 and LGN of cats reared in normal visual environment. The values will be compared to those of cats of corresponding ages, but reared in complete darkness (onset of CP for binocular vision prevented) or reared in darkness followed by rearing in the light (onset of CP delayed). In this way, I expect that the biochemical events pertinent to the CP will be delayed for as long as the animal is in the dark, and thus be made discriminable amongst all other biochemical events associated with general growth. My preliminary data suggest that during normal development, cAMP metabolism stimulated by the hormones rise dramatically after birth and plateau around the fourth month. Binocular cells in the cortex diminish in number irreversibly following monocular deprivation (MD) during the CP. Sillito's data indicate that a GABA receptor antagonist can reverse the MD effect to some extent. Such data indicate that a better understanding of the types of synapses (excitatory, inhibitory, modulatory) altered by experience during the CP is crucial for understanding the mechanism of visual plasticity. Thus, Kuhar method autoradiography will be done on serial sections of visual cortex and LGN of cats MDed during the CP so as to be able to visualize the distribution pattern of receptor sites of transmitters within the ocular dominance columns and LGN laminae. Further, the distribution pattern of two candidates to alter plasticity, cAMP and calmodulin (which activate the enzymes involved in cAMP metabolism) will be examined by the Kuhar method.